The present invention generally relates to an apparatus for processing a sample used to manufacture a semiconductor device. More specifically, the present invention is directed to an apparatus capable of performing either an etching process operation or a film forming process operation in a high efficiency and in high precision with respect to various sorts of films such as a silicon film and a silicon oxide film, which are formed on a semiconductor wafer surface having a substrate shape, while the semiconductor wafer corresponds to a sample which should be processed by using plasma.
As typical example as to the previously explained processing apparatus used to manufacture semiconductor devices, the below-mentioned plasma etching apparatus have been provided. That is, while resists are employed as masks which have been patterned on substrates such as semiconductor wafers by way of lithography techniques, films such as silicon films and silicon oxide films which have been formed on upper planes of these substrates and constitute structural materials of semiconductor devices are plasma-processed by using plasma generated in processing chambers which are arranged in the plasma etching apparatus under high vacuum condition. In plasma etching processes executed in such apparatus, processing gas induced into the processing chambers arranged in the vacuum vessels is processed by electric fields processed by the supplied high frequency electric power so as to generate plasma; and surfaces of substrates corresponding to sample to be processed are exposed by the generated plasma, so that films of the samples to be processed are etching-processed on the substrates.
When this etching process is carried out, since high frequency electric power is supplied to a lower electrode arranged within a sample table on which a sample corresponding to a material to be processed is mounted on this upper plane, a potential is formed also on this sample by the high frequency electric power, charged particles contained in plasma are induced to the surface side of the sample so as to increase a processing efficiency, so that a high speed processing operation can be carried out. In this case, while the above-explained sample is being exposed by the plasma, the high frequency electric power is further applied to the lower electrode, so that the sample is heated. On the other hand, a processed shape of a surface of a sample and an etching process characteristic such as an etching speed are largely influenced by temperatures (temperatures of film surface of process subject) on this sample surface. As a result, in order to achieve a desirable etching processed subject, surface temperatures of the processing subject must be controlled within proper temperature ranges. Accordingly, a sample mounting unit for mounting thereon samples have been mounted on the above-described conventional processing apparatus, for example, a unit for controlling temperatures of samples (e.g., samples are cooled) have been provided within sample tables.
In particular, in an etching process operation of insulating films which are typically known as a silicon oxide film, generally speaking, higher electric power is applied to a lower electrode, as compared with electric power used in the case that gate films such as a metal film and a silicon film are etched. For example, such an electric power higher than, or equal to 1.5 W/cm2 per a unit area of a sample is applied to the lower electrode. Furthermore, very recently, in order to realize processing operations in higher speeds, high frequency electric power higher than, or equal to 10 W/cm2 is required to be applied. In such a case that the above-described higher electric power is applied to either the lower electrode or the sample, such a cooling unit capable of cooling either a sample table or a wafer in a higher efficiency is required. As a cooling unit meeting this requirement, the following technical idea may be conceived. That is, either the sample table or the sample may be cooled by a refrigerating cycle which contains a coolant path within the sample table, and is constituted by using a compressor, a condenser, an expansion valve in addition to this coolant path.
As this conventional technical idea, such a system is disclosed in JP-A-2005-089864. This conventional technique discloses that while a path through which a heat exchanging medium (coolant) flows is arranged inside a sample table for mounting a sample within a processing chamber and this path corresponds to such path for constituting a refrigerating cycle, the coolant is evaporated within this path and is directly expanded to emit latent heat. As a result, the expanded coolant performs a heat exchange with the sample table and the sample mounted on this sample table in order to cool the temperature of the sample table and the temperature of the sample. In other words, in this conventional technique, either the sample table or the path for the coolant within the sample table may function as an evaporator which is equal to a heat exchanger of the refrigerating cycle.